1. Field of the Invention
The present invention relates to an eccentric roller control apparatus which is capable of controlling a depressing position of a pair of upper and lower back-up rolls according to the eccentricity of the back-up rolls in order to eliminate the adverse effect caused by the eccentric back-up rolls.
2. Description of the Prior Art
FIG. 3 is a block diagram showing a conventional eccentric roller control apparatus connected to a normal rolling machine to be controlled by the apparatus itself.
As shown, a rolling machine 1 provides an upper working roller 3T and a lower working roller 3B for rolling a material 2, an upper back-up roller 4T and a lower back-up roller 4B provided outside of the rollers 3T and 3B, a depressor 5W for driving the side of the lower back-up roller 4B in such a manner to change a gap between the lower working roller 4B and the lower back-up roller 3B, and a depressor 5D for driving the driving side of the rollers 4B and 3B. The depressors 5W and 5D are controlled by depressor control devices 6W and 6D, respectively.
In order to eliminate the adverse effect caused by the eccentric rollers 4T and 4B, the depressing weights placed on the working side and the driving side are sensed by weight sensors 7W and 7D, respectively. The rotary angles of the upper roller 4T and the lower roller 4B are also sensed by angle sensors 8T and 8B, respectively. The sensed depressed weights are added to each other by a weight adder 11. The weight adder 11 outputs the added weights. An eccentricity sensor 12 serves to sense the eccentricity amounts of the upper and the lower back-up rollers 4T and 4B, based on the added weights and the rotary angle sensed by the angle sensors 8T and 8B. A depression operating unit 13 serves to operate the controlled depressing amount, based on the sensed eccentricity amounts and the rotary angles sensed by the sensors 8T and 8B.
FIG. 4 is a block diagram showing the eccentricity sensor 12. The sensor 12 is arranged to have a weight lock-on unit 121 for storing the added weights as being interlocked with the rotary angle of the lower back-up roller 4B and calculating an average value, a weight deviation operating unit 122 for calculating a deviation of this average value to the added weights before averaging, a weight-to-gap converter 123 for calculating a gap deviation corresponding to the calculated weighted deviation, and an eccentricity analyzing unit 124 for calculating an amplitude as the eccentricity of the roller according to the outputs of the angle sensors 8T and 8B.
Then, the description will be directed to the operation of the eccentric roller control apparatus.
When the rolling machine 1 operates to roll the material 2, assuming that one or both of the upper and the lower back-up rollers 4T and 4B are eccentric, the width of the material 2 is not made uniform. To eliminate the adverse effect caused by the eccentric rollers, the weight sensors 7W and 7D serve to sense the depressed weights of the working side and the driving side and the angle sensors 8T and 8B serve to sense the rotary angle of the upper and the lower back-up rollers 4T and 4B, respectively.
Based on the sensed signals of the weight sensors 7W and 7D, the weight adder 11 performs the following operation: EQU P=P.sub.W +P.sub.D ( 1)
wherein P is an added weight [ton], P.sub.W is a depressed weight of the working side [ton], and P.sub.D is a depressed weight of the driving side [ton].
The eccentricity sensor 12 serves to calculate the amplitudes A.sub.Tn and B.sub.Tn [mm] of the eccentricity amount of the upper back-up roller 4T, based on the added weight P, the rotary angle .THETA..sub.T [rad] of the upper back-up roller 4T, and the rotary angle .THETA..sub.B [rad] of the lower back-up roller 4B.
In this case, the weight lock-on unit 121 composing the eccentricity sensor 12 serves to calculate an average value P.sub.L [ton] during one rotation of the lower back-up roller 4B from the starting point of the eccentricity amount in response to the added weight P and the rotary angle .THETA..sub.T of the lower back-up roller 4B. This average value P.sub.L is referred to as a lock-on value. The weight deviation operating unit 122 serves to obtain the weight deviation .DELTA.P [ton] from the following expression, based on the added weight P and the lock-on value P.sub.L. EQU .DELTA.P=P-P.sub.L ( 2)
The weight-gap converter 123 serves to calculate a gap deviation AS corresponding to the weight deviation .DELTA.P by the following expression. EQU .DELTA.S=-(M+m)..DELTA.P/(M.m) (3)
wherein M is a mill constant and m is a plastic coefficient.
The eccentricity analyzing unit 124 serves to accept this gap deviation AS, the rotary angles .THETA..sub.T, .THETA..sub.B of the upper and the lower back-up rollers and perform the fast Fourier transformation with respect to the input values for deriving an amplitude A.sub.Tn (an n-degree cosine component) of the deviation of the eccentricity of the upper back-up roller 4T, an amplitude B.sub.Tn (n-degree sin component) [mm], and amplitudes A.sub.Bn and B.sub.Bn of the eccentricity of the lower back-up roller 4B, based on those accepted values. The deviation .DELTA.S.sub.E [mm] corresponding to each of these amplitudes can be represented by the following expression. ##EQU1##
With the foregoing process, the eccentricity sensor 12 serves to calculate the amplitudes A.sub.Tn, B.sub.Tn, A.sub.Bn and B.sub.Bn of the eccentricity as the eccentricity of the upper or the lower back-up roller 4T or 4B.
Next, the depression operating unit 13 serves to accept the amplitudes A.sub.Tn, B.sub.Tn, A.sub.Bn and B.sub.Bn of the eccentricity of the upper or the lower back-up roller and the rotary angles .THETA..sub.T and .THETA..sub.B of the upper and lower back-up rollers sensed by the angle sensors 8T and 8B and calculate the depressing amount .DELTA.S.sub.CW of the working side and the depressing amount .DELTA.S.sub.CD of the driving side based on the accepted values. Then, the calculated values are sent to the depressor control devices 6W and 6D. ##EQU2## wherein T.sub.H is a time constant of the depressors 5W and 5B [sec].
Then, the depressor control device 6W serves to drive the depressor 5W according to the depressing control amount .DELTA.S.sub.CW of the working side and control each gap of the work sides of the upper and the lower working rollers 3T and 3B. Likewise, the depressor control device 6D serves to drive the depressor 5D according to the depressing control amount .DELTA.S.sub.CD of the driving side so as to control each gap of the driving sides of the upper and the lower working rollers 3T and 3B.
As described above, the conventional eccentric roller control apparatus is arranged to eliminate only an average value of each roller eccentricity amount of the working side and the driving side. This arrangement makes it impossible to completely eliminate the adverse effect of the roller eccentricity against a product profile, resulting in the lowering of a product quality.